ipc/msg.c

   1 /*
   2  * linux/ipc/msg.c
   3  * Copyright (C) 1992 Krishna Balasubramanian
   4  *
   5  * Removed all the remaining kerneld mess
   6  * Catch the -EFAULT stuff properly
   7  * Use GFP_KERNEL for messages as in 1.2
   8  * Fixed up the unchecked user space derefs
   9  * Copyright (C) 1998 Alan Cox & Andi Kleen
  10  *
  11  * /proc/sysvipc/msg support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
  12  *
  13  * mostly rewritten, threaded and wake-one semantics added
  14  * MSGMAX limit removed, sysctl's added
  15  * (c) 1999 Manfred Spraul <manfreds@colorfullife.com>
  16  */
  17
  18 #include <linux/config.h>
  19 #include <linux/slab.h>
  20 #include <linux/msg.h>
  21 #include <linux/spinlock.h>
  22 #include <linux/init.h>
  23 #include <linux/proc_fs.h>
  24 #include <linux/list.h>
  25 #include <linux/security.h>
  26 #include <linux/sched.h>
  27 #include <asm/current.h>
  28 #include <asm/uaccess.h>
  29 #include "util.h"
  30
  31 /* sysctl: */
  32 int msg_ctlmax = MSGMAX;
  33 int msg_ctlmnb = MSGMNB;
  34 int msg_ctlmni = MSGMNI;
  35
  36 /* one msg_receiver structure for each sleeping receiver */
  37 struct msg_receiver {
  38         struct list_head r_list;
  39         struct task_struct* r_tsk;
  40
  41         int r_mode;
  42         long r_msgtype;
  43         long r_maxsize;
  44
  45         struct msg_msg* volatile r_msg;
  46 };
  47
  48 /* one msg_sender for each sleeping sender */
  49 struct msg_sender {
  50         struct list_head list;
  51         struct task_struct* tsk;
  52 };
  53
  54 struct msg_msgseg {
  55         struct msg_msgseg* next;
  56         /* the next part of the message follows immediately */
  57 };
  58
  59 #define SEARCH_ANY              1
  60 #define SEARCH_EQUAL            2
  61 #define SEARCH_NOTEQUAL         3
  62 #define SEARCH_LESSEQUAL        4
  63
  64 static atomic_t msg_bytes = ATOMIC_INIT(0);
  65 static atomic_t msg_hdrs = ATOMIC_INIT(0);
  66
  67 static struct ipc_ids msg_ids;
  68
  69 #define msg_lock(id)    ((struct msg_queue*)ipc_lock(&msg_ids,id))
  70 #define msg_unlock(msq) ipc_unlock(&(msq)->q_perm)
  71 #define msg_rmid(id)    ((struct msg_queue*)ipc_rmid(&msg_ids,id))
  72 #define msg_checkid(msq, msgid) \
  73         ipc_checkid(&msg_ids,&msq->q_perm,msgid)
  74 #define msg_buildid(id, seq) \
  75         ipc_buildid(&msg_ids, id, seq)
  76
  77 static void freeque (struct msg_queue *msq, int id);
  78 static int newque (key_t key, int msgflg);
  79 #ifdef CONFIG_PROC_FS
  80 static int sysvipc_msg_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data);
  81 #endif
  82
  83 void __init msg_init (void)
  84 {
  85         ipc_init_ids(&msg_ids,msg_ctlmni);
  86
  87 #ifdef CONFIG_PROC_FS
  88         create_proc_read_entry("sysvipc/msg", 0, 0, sysvipc_msg_read_proc, NULL);
  89 #endif
  90 }
  91
  92 static int newque (key_t key, int msgflg)
  93 {
  94         int id;
  95         int retval;
  96         struct msg_queue *msq;
  97
  98         msq  = ipc_rcu_alloc(sizeof(*msq));
  99         if (!msq)
 100                 return -ENOMEM;
 101
 102         msq->q_perm.mode = (msgflg & S_IRWXUGO);
 103         msq->q_perm.key = key;
 104
 105         msq->q_perm.security = NULL;
 106         retval = security_msg_queue_alloc(msq);
 107         if (retval) {
 108                 ipc_rcu_free(msq, sizeof(*msq));
 109                 return retval;
 110         }
 111
 112         id = ipc_addid(&msg_ids, &msq->q_perm, msg_ctlmni);
 113         if(id == -1) {
 114                 security_msg_queue_free(msq);
 115                 ipc_rcu_free(msq, sizeof(*msq));
 116                 return -ENOSPC;
 117         }
 118
 119         msq->q_stime = msq->q_rtime = 0;
 120         msq->q_ctime = get_seconds();
 121         msq->q_cbytes = msq->q_qnum = 0;
 122         msq->q_qbytes = msg_ctlmnb;
 123         msq->q_lspid = msq->q_lrpid = 0;
 124         INIT_LIST_HEAD(&msq->q_messages);
 125         INIT_LIST_HEAD(&msq->q_receivers);
 126         INIT_LIST_HEAD(&msq->q_senders);
 127         msg_unlock(msq);
 128
 129         return msg_buildid(id,msq->q_perm.seq);
 130 }
 131
 132 static void free_msg(struct msg_msg* msg)
 133 {
 134         struct msg_msgseg* seg;
 135
 136         security_msg_msg_free(msg);
 137
 138         seg = msg->next;
 139         kfree(msg);
 140         while(seg != NULL) {
 141                 struct msg_msgseg* tmp = seg->next;
 142                 kfree(seg);
 143                 seg = tmp;
 144         }
 145 }
 146
 147 static struct msg_msg* load_msg(void* src, int len)
 148 {
 149         struct msg_msg* msg;
 150         struct msg_msgseg** pseg;
 151         int err;
 152         int alen;
 153
 154         alen = len;
 155         if(alen > DATALEN_MSG)
 156                 alen = DATALEN_MSG;
 157
 158         msg = (struct msg_msg *) kmalloc (sizeof(*msg) + alen, GFP_KERNEL);
 159         if(msg==NULL)
 160                 return ERR_PTR(-ENOMEM);
 161
 162         msg->next = NULL;
 163         msg->security = NULL;
 164
 165         if (copy_from_user(msg+1, src, alen)) {
 166                 err = -EFAULT;
 167                 goto out_err;
 168         }
 169
 170         len -= alen;
 171         src = ((char*)src)+alen;
 172         pseg = &msg->next;
 173         while(len > 0) {
 174                 struct msg_msgseg* seg;
 175                 alen = len;
 176                 if(alen > DATALEN_SEG)
 177                         alen = DATALEN_SEG;
 178                 seg = (struct msg_msgseg *) kmalloc (sizeof(*seg) + alen, GFP_KERNEL);
 179                 if(seg==NULL) {
 180                         err=-ENOMEM;
 181                         goto out_err;
 182                 }
 183                 *pseg = seg;
 184                 seg->next = NULL;
 185                 if(copy_from_user (seg+1, src, alen)) {
 186                         err = -EFAULT;
 187                         goto out_err;
 188                 }
 189                 pseg = &seg->next;
 190                 len -= alen;
 191                 src = ((char*)src)+alen;
 192         }
 193
 194         err = security_msg_msg_alloc(msg);
 195         if (err)
 196                 goto out_err;
 197
 198         return msg;
 199
 200 out_err:
 201         free_msg(msg);
 202         return ERR_PTR(err);
 203 }
 204
 205 static int store_msg(void* dest, struct msg_msg* msg, int len)
 206 {
 207         int alen;
 208         struct msg_msgseg *seg;
 209
 210         alen = len;
 211         if(alen > DATALEN_MSG)
 212                 alen = DATALEN_MSG;
 213         if(copy_to_user (dest, msg+1, alen))
 214                 return -1;
 215
 216         len -= alen;
 217         dest = ((char*)dest)+alen;
 218         seg = msg->next;
 219         while(len > 0) {
 220                 alen = len;
 221                 if(alen > DATALEN_SEG)
 222                         alen = DATALEN_SEG;
 223                 if(copy_to_user (dest, seg+1, alen))
 224                         return -1;
 225                 len -= alen;
 226                 dest = ((char*)dest)+alen;
 227                 seg=seg->next;
 228         }
 229         return 0;
 230 }
 231
 232 static inline void ss_add(struct msg_queue* msq, struct msg_sender* mss)
 233 {
 234         mss->tsk=current;
 235         current->state=TASK_INTERRUPTIBLE;
 236         list_add_tail(&mss->list,&msq->q_senders);
 237 }
 238
 239 static inline void ss_del(struct msg_sender* mss)
 240 {
 241         if(mss->list.next != NULL)
 242                 list_del(&mss->list);
 243 }
 244
 245 static void ss_wakeup(struct list_head* h, int kill)
 246 {
 247         struct list_head *tmp;
 248
 249         tmp = h->next;
 250         while (tmp != h) {
 251                 struct msg_sender* mss;
 252
 253                 mss = list_entry(tmp,struct msg_sender,list);
 254                 tmp = tmp->next;
 255                 if(kill)
 256                         mss->list.next=NULL;
 257                 wake_up_process(mss->tsk);
 258         }
 259 }
 260
 261 static void expunge_all(struct msg_queue* msq, int res)
 262 {
 263         struct list_head *tmp;
 264
 265         tmp = msq->q_receivers.next;
 266         while (tmp != &msq->q_receivers) {
 267                 struct msg_receiver* msr;
 268
 269                 msr = list_entry(tmp,struct msg_receiver,r_list);
 270                 tmp = tmp->next;
 271                 msr->r_msg = ERR_PTR(res);
 272                 wake_up_process(msr->r_tsk);
 273         }
 274 }
 275 /*
 276  * freeque() wakes up waiters on the sender and receiver waiting queue,
 277  * removes the message queue from message queue ID
 278  * array, and cleans up all the messages associated with this queue.
 279  *
 280  * msg_ids.sem and the spinlock for this message queue is hold
 281  * before freeque() is called. msg_ids.sem remains locked on exit.
 282  */
 283 static void freeque (struct msg_queue *msq, int id)
 284 {
 285         struct list_head *tmp;
 286
 287         expunge_all(msq,-EIDRM);
 288         ss_wakeup(&msq->q_senders,1);
 289         msq = msg_rmid(id);
 290         msg_unlock(msq);
 291
 292         tmp = msq->q_messages.next;
 293         while(tmp != &msq->q_messages) {
 294                 struct msg_msg* msg = list_entry(tmp,struct msg_msg,m_list);
 295                 tmp = tmp->next;
 296                 atomic_dec(&msg_hdrs);
 297                 free_msg(msg);
 298         }
 299         atomic_sub(msq->q_cbytes, &msg_bytes);
 300         security_msg_queue_free(msq);
 301         ipc_rcu_free(msq, sizeof(struct msg_queue));
 302 }
 303
 304 asmlinkage long sys_msgget (key_t key, int msgflg)
 305 {
 306         int id, ret = -EPERM;
 307         struct msg_queue *msq;
 308
 309         down(&msg_ids.sem);
 310         if (key == IPC_PRIVATE)
 311                 ret = newque(key, msgflg);
 312         else if ((id = ipc_findkey(&msg_ids, key)) == -1) { /* key not used */
 313                 if (!(msgflg & IPC_CREAT))
 314                         ret = -ENOENT;
 315                 else
 316                         ret = newque(key, msgflg);
 317         } else if (msgflg & IPC_CREAT && msgflg & IPC_EXCL) {
 318                 ret = -EEXIST;
 319         } else {
 320                 msq = msg_lock(id);
 321                 if(msq==NULL)
 322                         BUG();
 323                 if (ipcperms(&msq->q_perm, msgflg))
 324                         ret = -EACCES;
 325                 else {
 326                         int qid = msg_buildid(id, msq->q_perm.seq);
 327                         ret = security_msg_queue_associate(msq, msgflg);
 328                         if (!ret)
 329                                 ret = qid;
 330                 }
 331                 msg_unlock(msq);
 332         }
 333         up(&msg_ids.sem);
 334         return ret;
 335 }
 336
 337 static inline unsigned long copy_msqid_to_user(void *buf, struct msqid64_ds *in, int version)
 338 {
 339         switch(version) {
 340         case IPC_64:
 341                 return copy_to_user (buf, in, sizeof(*in));
 342         case IPC_OLD:
 343             {
 344                 struct msqid_ds out;
 345
 346                 memset(&out,0,sizeof(out));
 347
 348                 ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
 349
 350                 out.msg_stime           = in->msg_stime;
 351                 out.msg_rtime           = in->msg_rtime;
 352                 out.msg_ctime           = in->msg_ctime;
 353
 354                 if(in->msg_cbytes > USHRT_MAX)
 355                         out.msg_cbytes  = USHRT_MAX;
 356                 else
 357                         out.msg_cbytes  = in->msg_cbytes;
 358                 out.msg_lcbytes         = in->msg_cbytes;
 359
 360                 if(in->msg_qnum > USHRT_MAX)
 361                         out.msg_qnum    = USHRT_MAX;
 362                 else
 363                         out.msg_qnum    = in->msg_qnum;
 364
 365                 if(in->msg_qbytes > USHRT_MAX)
 366                         out.msg_qbytes  = USHRT_MAX;
 367                 else
 368                         out.msg_qbytes  = in->msg_qbytes;
 369                 out.msg_lqbytes         = in->msg_qbytes;
 370
 371                 out.msg_lspid           = in->msg_lspid;
 372                 out.msg_lrpid           = in->msg_lrpid;
 373
 374                 return copy_to_user (buf, &out, sizeof(out));
 375             }
 376         default:
 377                 return -EINVAL;
 378         }
 379 }
 380
 381 struct msq_setbuf {
 382         unsigned long   qbytes;
 383         uid_t           uid;
 384         gid_t           gid;
 385         mode_t          mode;
 386 };
 387
 388 static inline unsigned long copy_msqid_from_user(struct msq_setbuf *out, void *buf, int version)
 389 {
 390         switch(version) {
 391         case IPC_64:
 392             {
 393                 struct msqid64_ds tbuf;
 394
 395                 if (copy_from_user (&tbuf, buf, sizeof (tbuf)))
 396                         return -EFAULT;
 397
 398                 out->qbytes             = tbuf.msg_qbytes;
 399                 out->uid                = tbuf.msg_perm.uid;
 400                 out->gid                = tbuf.msg_perm.gid;
 401                 out->mode               = tbuf.msg_perm.mode;
 402
 403                 return 0;
 404             }
 405         case IPC_OLD:
 406             {
 407                 struct msqid_ds tbuf_old;
 408
 409                 if (copy_from_user (&tbuf_old, buf, sizeof (tbuf_old)))
 410                         return -EFAULT;
 411
 412                 out->uid                = tbuf_old.msg_perm.uid;
 413                 out->gid                = tbuf_old.msg_perm.gid;
 414                 out->mode               = tbuf_old.msg_perm.mode;
 415
 416                 if(tbuf_old.msg_qbytes == 0)
 417                         out->qbytes     = tbuf_old.msg_lqbytes;
 418                 else
 419                         out->qbytes     = tbuf_old.msg_qbytes;
 420
 421                 return 0;
 422             }
 423         default:
 424                 return -EINVAL;
 425         }
 426 }
 427
 428 asmlinkage long sys_msgctl (int msqid, int cmd, struct msqid_ds *buf)
 429 {
 430         int err, version;
 431         struct msg_queue *msq;
 432         struct msq_setbuf setbuf;
 433         struct kern_ipc_perm *ipcp;
 434
 435         if (msqid < 0 || cmd < 0)
 436                 return -EINVAL;
 437
 438         version = ipc_parse_version(&cmd);
 439
 440         switch (cmd) {
 441         case IPC_INFO:
 442         case MSG_INFO:
 443         {
 444                 struct msginfo msginfo;
 445                 int max_id;
 446                 if (!buf)
 447                         return -EFAULT;
 448                 /* We must not return kernel stack data.
 449                  * due to padding, it's not enough
 450                  * to set all member fields.
 451                  */
 452
 453                 err = security_msg_queue_msgctl(NULL, cmd);
 454                 if (err)
 455                         return err;
 456
 457                 memset(&msginfo,0,sizeof(msginfo));
 458                 msginfo.msgmni = msg_ctlmni;
 459                 msginfo.msgmax = msg_ctlmax;
 460                 msginfo.msgmnb = msg_ctlmnb;
 461                 msginfo.msgssz = MSGSSZ;
 462                 msginfo.msgseg = MSGSEG;
 463                 down(&msg_ids.sem);
 464                 if (cmd == MSG_INFO) {
 465                         msginfo.msgpool = msg_ids.in_use;
 466                         msginfo.msgmap = atomic_read(&msg_hdrs);
 467                         msginfo.msgtql = atomic_read(&msg_bytes);
 468                 } else {
 469                         msginfo.msgmap = MSGMAP;
 470                         msginfo.msgpool = MSGPOOL;
 471                         msginfo.msgtql = MSGTQL;
 472                 }
 473                 max_id = msg_ids.max_id;
 474                 up(&msg_ids.sem);
 475                 if (copy_to_user (buf, &msginfo, sizeof(struct msginfo)))
 476                         return -EFAULT;
 477                 return (max_id < 0) ? 0: max_id;
 478         }
 479         case MSG_STAT:
 480         case IPC_STAT:
 481         {
 482                 struct msqid64_ds tbuf;
 483                 int success_return;
 484                 if (!buf)
 485                         return -EFAULT;
 486                 if(cmd == MSG_STAT && msqid >= msg_ids.size)
 487                         return -EINVAL;
 488
 489                 memset(&tbuf,0,sizeof(tbuf));
 490
 491                 msq = msg_lock(msqid);
 492                 if (msq == NULL)
 493                         return -EINVAL;
 494
 495                 if(cmd == MSG_STAT) {
 496                         success_return = msg_buildid(msqid, msq->q_perm.seq);
 497                 } else {
 498                         err = -EIDRM;
 499                         if (msg_checkid(msq,msqid))
 500                                 goto out_unlock;
 501                         success_return = 0;
 502                 }
 503                 err = -EACCES;
 504                 if (ipcperms (&msq->q_perm, S_IRUGO))
 505                         goto out_unlock;
 506
 507                 err = security_msg_queue_msgctl(msq, cmd);
 508                 if (err)
 509                         goto out_unlock;
 510
 511                 kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
 512                 tbuf.msg_stime  = msq->q_stime;
 513                 tbuf.msg_rtime  = msq->q_rtime;
 514                 tbuf.msg_ctime  = msq->q_ctime;
 515                 tbuf.msg_cbytes = msq->q_cbytes;
 516                 tbuf.msg_qnum   = msq->q_qnum;
 517                 tbuf.msg_qbytes = msq->q_qbytes;
 518                 tbuf.msg_lspid  = msq->q_lspid;
 519                 tbuf.msg_lrpid  = msq->q_lrpid;
 520                 msg_unlock(msq);
 521                 if (copy_msqid_to_user(buf, &tbuf, version))
 522                         return -EFAULT;
 523                 return success_return;
 524         }
 525         case IPC_SET:
 526                 if (!buf)
 527                         return -EFAULT;
 528                 if (copy_msqid_from_user (&setbuf, buf, version))
 529                         return -EFAULT;
 530                 break;
 531         case IPC_RMID:
 532                 break;
 533         default:
 534                 return  -EINVAL;
 535         }
 536
 537         down(&msg_ids.sem);
 538         msq = msg_lock(msqid);
 539         err=-EINVAL;
 540         if (msq == NULL)
 541                 goto out_up;
 542
 543         err = -EIDRM;
 544         if (msg_checkid(msq,msqid))
 545                 goto out_unlock_up;
 546         ipcp = &msq->q_perm;
 547         err = -EPERM;
 548         if (current->euid != ipcp->cuid &&
 549             current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN))
 550             /* We _could_ check for CAP_CHOWN above, but we don't */
 551                 goto out_unlock_up;
 552
 553         err = security_msg_queue_msgctl(msq, cmd);
 554         if (err)
 555                 goto out_unlock_up;
 556
 557         switch (cmd) {
 558         case IPC_SET:
 559         {
 560                 if (setbuf.qbytes > msg_ctlmnb && !capable(CAP_SYS_RESOURCE))
 561                         goto out_unlock_up;
 562
 563                 msq->q_qbytes = setbuf.qbytes;
 564
 565                 ipcp->uid = setbuf.uid;
 566                 ipcp->gid = setbuf.gid;
 567                 ipcp->mode = (ipcp->mode & ~S_IRWXUGO) |
 568                         (S_IRWXUGO & setbuf.mode);
 569                 msq->q_ctime = get_seconds();
 570                 /* sleeping receivers might be excluded by
 571                  * stricter permissions.
 572                  */
 573                 expunge_all(msq,-EAGAIN);
 574                 /* sleeping senders might be able to send
 575                  * due to a larger queue size.
 576                  */
 577                 ss_wakeup(&msq->q_senders,0);
 578                 msg_unlock(msq);
 579                 break;
 580         }
 581         case IPC_RMID:
 582                 freeque (msq, msqid);
 583                 break;
 584         }
 585         err = 0;
 586 out_up:
 587         up(&msg_ids.sem);
 588         return err;
 589 out_unlock_up:
 590         msg_unlock(msq);
 591         goto out_up;
 592 out_unlock:
 593         msg_unlock(msq);
 594         return err;
 595 }
 596
 597 static int testmsg(struct msg_msg* msg,long type,int mode)
 598 {
 599         switch(mode)
 600         {
 601                 case SEARCH_ANY:
 602                         return 1;
 603                 case SEARCH_LESSEQUAL:
 604                         if(msg->m_type <=type)
 605                                 return 1;
 606                         break;
 607                 case SEARCH_EQUAL:
 608                         if(msg->m_type == type)
 609                                 return 1;
 610                         break;
 611                 case SEARCH_NOTEQUAL:
 612                         if(msg->m_type != type)
 613                                 return 1;
 614                         break;
 615         }
 616         return 0;
 617 }
 618
 619 static inline int pipelined_send(struct msg_queue* msq, struct msg_msg* msg)
 620 {
 621         struct list_head* tmp;
 622
 623         tmp = msq->q_receivers.next;
 624         while (tmp != &msq->q_receivers) {
 625                 struct msg_receiver* msr;
 626                 msr = list_entry(tmp,struct msg_receiver,r_list);
 627                 tmp = tmp->next;
 628                 if(testmsg(msg,msr->r_msgtype,msr->r_mode) &&
 629                    !security_msg_queue_msgrcv(msq, msg, msr->r_tsk, msr->r_msgtype, msr->r_mode)) {
 630                         list_del(&msr->r_list);
 631                         if(msr->r_maxsize < msg->m_ts) {
 632                                 msr->r_msg = ERR_PTR(-E2BIG);
 633                                 wake_up_process(msr->r_tsk);
 634                         } else {
 635                                 msr->r_msg = msg;
 636                                 msq->q_lrpid = msr->r_tsk->pid;
 637                                 msq->q_rtime = get_seconds();
 638                                 wake_up_process(msr->r_tsk);
 639                                 return 1;
 640                         }
 641                 }
 642         }
 643         return 0;
 644 }
 645
 646 asmlinkage long sys_msgsnd (int msqid, struct msgbuf *msgp, size_t msgsz, int msgflg)
 647 {
 648         struct msg_queue *msq;
 649         struct msg_msg *msg;
 650         long mtype;
 651         int err;
 652
 653         if (msgsz > msg_ctlmax || (long) msgsz < 0 || msqid < 0)
 654                 return -EINVAL;
 655         if (get_user(mtype, &msgp->mtype))
 656                 return -EFAULT;
 657         if (mtype < 1)
 658                 return -EINVAL;
 659
 660         msg = load_msg(msgp->mtext, msgsz);
 661         if(IS_ERR(msg))
 662                 return PTR_ERR(msg);
 663
 664         msg->m_type = mtype;
 665         msg->m_ts = msgsz;
 666
 667         msq = msg_lock(msqid);
 668         err=-EINVAL;
 669         if(msq==NULL)
 670                 goto out_free;
 671 retry:
 672         err= -EIDRM;
 673         if (msg_checkid(msq,msqid))
 674                 goto out_unlock_free;
 675
 676         err=-EACCES;
 677         if (ipcperms(&msq->q_perm, S_IWUGO))
 678                 goto out_unlock_free;
 679
 680         err = security_msg_queue_msgsnd(msq, msg, msgflg);
 681         if (err)
 682                 goto out_unlock_free;
 683
 684         if(msgsz + msq->q_cbytes > msq->q_qbytes ||
 685                 1 + msq->q_qnum > msq->q_qbytes) {
 686                 struct msg_sender s;
 687
 688                 if(msgflg&IPC_NOWAIT) {
 689                         err=-EAGAIN;
 690                         goto out_unlock_free;
 691                 }
 692                 ss_add(msq, &s);
 693                 msg_unlock(msq);
 694                 schedule();
 695                 current->state= TASK_RUNNING;
 696
 697                 msq = msg_lock(msqid);
 698                 err = -EIDRM;
 699                 if(msq==NULL)
 700                         goto out_free;
 701                 ss_del(&s);
 702
 703                 if (signal_pending(current)) {
 704                         err=-EINTR;
 705                         goto out_unlock_free;
 706                 }
 707                 goto retry;
 708         }
 709
 710         msq->q_lspid = current->tgid;
 711         msq->q_stime = get_seconds();
 712
 713         if(!pipelined_send(msq,msg)) {
 714                 /* noone is waiting for this message, enqueue it */
 715                 list_add_tail(&msg->m_list,&msq->q_messages);
 716                 msq->q_cbytes += msgsz;
 717                 msq->q_qnum++;
 718                 atomic_add(msgsz,&msg_bytes);
 719                 atomic_inc(&msg_hdrs);
 720         }
 721
 722         err = 0;
 723         msg = NULL;
 724
 725 out_unlock_free:
 726         msg_unlock(msq);
 727 out_free:
 728         if(msg!=NULL)
 729                 free_msg(msg);
 730         return err;
 731 }
 732
 733 static inline int convert_mode(long* msgtyp, int msgflg)
 734 {
 735         /*
 736          *  find message of correct type.
 737          *  msgtyp = 0 => get first.
 738          *  msgtyp > 0 => get first message of matching type.
 739          *  msgtyp < 0 => get message with least type must be < abs(msgtype).
 740          */
 741         if(*msgtyp==0)
 742                 return SEARCH_ANY;
 743         if(*msgtyp<0) {
 744                 *msgtyp=-(*msgtyp);
 745                 return SEARCH_LESSEQUAL;
 746         }
 747         if(msgflg & MSG_EXCEPT)
 748                 return SEARCH_NOTEQUAL;
 749         return SEARCH_EQUAL;
 750 }
 751
 752 asmlinkage long sys_msgrcv (int msqid, struct msgbuf *msgp, size_t msgsz,
 753                             long msgtyp, int msgflg)
 754 {
 755         struct msg_queue *msq;
 756         struct msg_receiver msr_d;
 757         struct list_head* tmp;
 758         struct msg_msg* msg, *found_msg;
 759         int err;
 760         int mode;
 761
 762         if (msqid < 0 || (long) msgsz < 0)
 763                 return -EINVAL;
 764         mode = convert_mode(&msgtyp,msgflg);
 765
 766         msq = msg_lock(msqid);
 767         if(msq==NULL)
 768                 return -EINVAL;
 769 retry:
 770         err = -EIDRM;
 771         if (msg_checkid(msq,msqid))
 772                 goto out_unlock;
 773
 774         err=-EACCES;
 775         if (ipcperms (&msq->q_perm, S_IRUGO))
 776                 goto out_unlock;
 777
 778         tmp = msq->q_messages.next;
 779         found_msg=NULL;
 780         while (tmp != &msq->q_messages) {
 781                 msg = list_entry(tmp,struct msg_msg,m_list);
 782                 if(testmsg(msg,msgtyp,mode) &&
 783                    !security_msg_queue_msgrcv(msq, msg, current, msgtyp, mode)) {
 784                         found_msg = msg;
 785                         if(mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
 786                                 found_msg=msg;
 787                                 msgtyp=msg->m_type-1;
 788                         } else {
 789                                 found_msg=msg;
 790                                 break;
 791                         }
 792                 }
 793                 tmp = tmp->next;
 794         }
 795         if(found_msg) {
 796                 msg=found_msg;
 797                 if ((msgsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
 798                         err=-E2BIG;
 799                         goto out_unlock;
 800                 }
 801                 list_del(&msg->m_list);
 802                 msq->q_qnum--;
 803                 msq->q_rtime = get_seconds();
 804                 msq->q_lrpid = current->tgid;
 805                 msq->q_cbytes -= msg->m_ts;
 806                 atomic_sub(msg->m_ts,&msg_bytes);
 807                 atomic_dec(&msg_hdrs);
 808                 ss_wakeup(&msq->q_senders,0);
 809                 msg_unlock(msq);
 810 out_success:
 811                 msgsz = (msgsz > msg->m_ts) ? msg->m_ts : msgsz;
 812                 if (put_user (msg->m_type, &msgp->mtype) ||
 813                     store_msg(msgp->mtext, msg, msgsz)) {
 814                             msgsz = -EFAULT;
 815                 }
 816                 free_msg(msg);
 817                 return msgsz;
 818         } else
 819         {
 820                 /* no message waiting. Prepare for pipelined
 821                  * receive.
 822                  */
 823                 if (msgflg & IPC_NOWAIT) {
 824                         err=-ENOMSG;
 825                         goto out_unlock;
 826                 }
 827                 list_add_tail(&msr_d.r_list,&msq->q_receivers);
 828                 msr_d.r_tsk = current;
 829                 msr_d.r_msgtype = msgtyp;
 830                 msr_d.r_mode = mode;
 831                 if(msgflg & MSG_NOERROR)
 832                         msr_d.r_maxsize = INT_MAX;
 833                  else
 834                         msr_d.r_maxsize = msgsz;
 835                 msr_d.r_msg = ERR_PTR(-EAGAIN);
 836                 current->state = TASK_INTERRUPTIBLE;
 837                 msg_unlock(msq);
 838
 839                 schedule();
 840
 841                 /*
 842                  * The below optimisation is buggy.  A sleeping thread that is
 843                  * woken up checks if it got a message and if so, copies it to
 844                  * userspace and just returns without taking any locks.
 845                  * But this return to user space can be faster than the message
 846                  * send, and if the receiver immediately exits the
 847                  * wake_up_process performed by the sender will oops.
 848                  */
 849 #if 0
 850                 msg = (struct msg_msg*) msr_d.r_msg;
 851                 if(!IS_ERR(msg))
 852                         goto out_success;
 853 #endif
 854
 855                 msq = msg_lock(msqid);
 856                 msg = (struct msg_msg*)msr_d.r_msg;
 857                 if(!IS_ERR(msg)) {
 858                         /* our message arived while we waited for
 859                          * the spinlock. Process it.
 860                          */
 861                         if(msq)
 862                                 msg_unlock(msq);
 863                         goto out_success;
 864                 }
 865                 err = PTR_ERR(msg);
 866                 if(err == -EAGAIN) {
 867                         if(!msq)
 868                                 BUG();
 869                         list_del(&msr_d.r_list);
 870                         if (signal_pending(current))
 871                                 err=-EINTR;
 872                          else
 873                                 goto retry;
 874                 }
 875         }
 876 out_unlock:
 877         if(msq)
 878                 msg_unlock(msq);
 879         return err;
 880 }
 881
 882 #ifdef CONFIG_PROC_FS
 883 static int sysvipc_msg_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data)
 884 {
 885         off_t pos = 0;
 886         off_t begin = 0;
 887         int i, len = 0;
 888
 889         down(&msg_ids.sem);
 890         len += sprintf(buffer, "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n");
 891
 892         for(i = 0; i <= msg_ids.max_id; i++) {
 893                 struct msg_queue * msq;
 894                 msq = msg_lock(i);
 895                 if(msq != NULL) {
 896                         len += sprintf(buffer + len, "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
 897                                 msq->q_perm.key,
 898                                 msg_buildid(i,msq->q_perm.seq),
 899                                 msq->q_perm.mode,
 900                                 msq->q_cbytes,
 901                                 msq->q_qnum,
 902                                 msq->q_lspid,
 903                                 msq->q_lrpid,
 904                                 msq->q_perm.uid,
 905                                 msq->q_perm.gid,
 906                                 msq->q_perm.cuid,
 907                                 msq->q_perm.cgid,
 908                                 msq->q_stime,
 909                                 msq->q_rtime,
 910                                 msq->q_ctime);
 911                         msg_unlock(msq);
 912
 913                         pos += len;
 914                         if(pos < offset) {
 915                                 len = 0;
 916                                 begin = pos;
 917                         }
 918                         if(pos > offset + length)
 919                                 goto done;
 920                 }
 921
 922         }
 923         *eof = 1;
 924 done:
 925         up(&msg_ids.sem);
 926         *start = buffer + (offset - begin);
 927         len -= (offset - begin);
 928         if(len > length)
 929                 len = length;
 930         if(len < 0)
 931                 len = 0;
 932         return len;
 933 }
 934 #endif